Application of broadband nonlinear targeted energy transfers for seismic mitigation of a shear frame: Computational results

In this work we show that it is possible to successfully apply the concept of nonlinear targeted energy transfer (TET) to seismic protection of structures; moreover, this passive strategy of seismic vibration control is found to be feasible and robust. We consider a three-story shear-frame structure, modeled as a three-degree-of-freedom system, subjected to four historic earthquakes as seismic excitation. Seismic mitigation is achieved by applying single or multiple nonlinear energy sinks (NESs) to the test structure. We study the performance and efficiency of the NESs through a set of evaluation criteria. First we consider a single vibro-impact NES (VI NES) applied to the top floor of the structure. In order to assess the robustness of the VI NES, the NES parameters are optimized for a specific seismic excitation (Kobe), and then tested against the three other earthquake records to demonstrate effectiveness of the NES for these cases as well. To further improve the effectiveness of the seismic mitigation, we then consider a system of two NESs-an NES with smooth nonlinearity at the top floor of the test structure and a VI NES at the bottom floor. We show that it is indeed possible to drastically reduce the structural seismic response (e.g., displacements, drifts, and accelerations) using this configuration.